Patent GB-495516-A (GB)
Title: Process for the separation of trimethylamine from mixtures with monomethylamine and dimethylamine
Filed: 1937-12-10
Abstract: Trimethylamine is separated from mixtures thereof with mono- or dimethylamine or both by selectively absorbing the mono- and/or dimethylamine in water at a temperature 10-75 DEG  C. below the boiling point of water at the pressure employed, which is preferably over 40 lb. per sq. in. above atmospheric.  In a preferred method of working, the mixture of methylamines is passed at an intermediate point into a column down which passes water at the desired temperature in quantities sufficient to dissolve substantially all the mono- and/or dimethylamine but insufficient to dissolve the whole mixture, whereby substantially pure trimethylamine passes out from the top of the column.  Examples describe the application of this preferred process to the treatment of various mixtures of the three methylamines, containing traces of water and methanol, the following temperatures and pressures being employed: 83 DEG  C. (at top of column) to 105 DEG  C. (in the pot) at 50 lb. per sq. in. above atmospheric pressure; 90-134 DEG  C. at 100 lb. per sq. in. above atmospheric pressure; and 108-144 DEG  C. at 150 lb. per sq. in. above atmospheric pressure.  A further example describes the absorption of a mixture of the three methylamines and a trace of ammonia in water at 79 DEG  C. under atmospheric pressure.  The Specification as open to inspection under Sect. 91 comprises also the separation of monomethylamine from dimethylamine by a similar process.  By working with water at temperatures down to 50 DEG  C. below its boiling point, dimethylamine is separated as the less soluble gas, whilst at temperatures from this point down to the boiling point of dimethylamine it is possible to separate monomethylamine as the less soluble gas.  This subject-matter does not appear in the Specification as accepted.ALSO:Trimethylamine is separated from mixtures thereof with mono- or dimethylamine or both, e.g. the mixtures obtained by passing methanol and ammonia over a dehydrating catalyst, by selectively absorbing the mono- or dimethylamine or both in water at a temperature from 10-75 DEG  C. below the boiling point of water at the pressure employed, which is preferably over 40 lb. per sq. in. above atmospheric.  In a preferred method of working, the mixture of methylamines is passed at an intermediate point into a column down which passes water at the desired temperature in quantities sufficient to dissolve substantially all the mono- and/or dimethylamine but insufficient to dissolve the whole mixture, whereby substantially pure trimethylamine passes out from the top of the column.  Examples describe the application of this preferred process to the treatment of various mixtures of the three methylamines containing traces of water and methanol, the following temperatures and pressures being employed: 83 DEG  C. (at top of column) to 105 DEG  C. (in the pot) at 50 lb. per sq. in. above atmospheric pressure; 90-134 DEG  C. at 100 lb. per sq. in. above atmospheric pressure; and 108-144 DEG  C. at 150 lb. per sq. in. above atmospheric pressure.  A further example describes the absorption of a mixture of the three methylamines and a trace of ammonia in water at 79 DEG  C. under atmospheric pressure.  The Specification as open to inspection under Sect. 91 comprises also the separation of monomethylamine from dimethylamine by a similar process.  By working with water at temperatures down to 50 DEG  C. below its boiling point, dimethylamine is separated as the less soluble gas, whilst at temperatures from this point down to the boiling point of dimethylamine, it is possible to separate monomethylamine as the less soluble gas.  This subject-matter does not appear in the Specification as accepted.